1. Field of the Invention
The present invention relates to composite metal and plastic fencing and, more particularly, to composite metal wire and plastic fence rail members.
2. Description of the Prior Art
Composite metal and plastic fencing is well-known in the art. Composite metal and plastic fencing is known as an inexpensive and safe alternative to other commonly employed materials used in the construction of fences such as wood and barbed wire. Wood suffers from the disadvantages that it is expensive to install and maintain and, further, that it has a tendency to weather and rot over time. Barbed wire fencing is a relatively low cost means for enclosing livestock areas. However, barbed wire fencing suffers from the disadvantage that its sharp barbs may cut or gouge the hide of valuable livestock animals such as horses.
One example of composite metal and plastic fencing found in the prior art is disclosed by U.S. Pat. No. 4,465,263 to Robbins, Jr. (hereinafter xe2x80x9cthe Robbins ""263 patentxe2x80x9d). The Robbins ""263 patent discloses a composite metal and plastic fence that includes at least two high tensile strength metal wires that are ensheathed in a plastic casing and affixed to posts or poles with clamps. In the Robbins ""263 patent, the two metal wires are spaced a distance apart and the plastic that encloses the wires also forms a web area extending between the wires.
U.S. Pat. No. 4,684,107 to Robbins, Jr. (hereinafter xe2x80x9cthe Robbins ""107 patentxe2x80x9d) discloses a composite metal and plastic fence which improves on the composite metal and plastic fence disclosed by the Robbins ""263 patent. The Robbins ""107 patent discloses a composite metal wire and plastic fence that is intended to improve the adhesion between the wires and the plastic covering layer. This is accomplished by roughening the exterior of the wires before the wires are ensheathed with extruded plastic.
U.S. Pat. No. 4,533,120 to Ruddock discloses fencing rail members in the form of a composite member which may be used as a substitute for wooden rails in fencing. The Ruddock patent discloses a composite member that includes a plurality of wire members that are spaced apart and coated by a synthetic resin material forming a web between the wires. Longitudinal ribs are formed on the webs to facilitate coiling of the fence rail members for storage or transit and to enhance the appearance of the fence rail members.
The above-discussed prior art suffers the disadvantage that when two adjacent coils of fencing are joined together by mechanically fastening the wires (such as with crimping sleeves), the plastic outer layer has a tendency to separate or pull apart from the underlying wires when the wires are tensioned. As a result, the wires may become exposed to potentially injure livestock. In addition, the exposed wires make the composite fencing unsightly. The above-discussed Robbins ""107 patent attempts to overcome this disadvantage by first abrading or roughening the wires to improve the connection between the wires and the surrounding plastic. However, the abrading can cause damage to the protective coating of the wires necessitating a topical coating of paint on the exposed or stripped wires before covering the wires with extruded plastic. The roughening of the exterior of the wires can cause the plastic coating to be prematurely worn, exposing the wire and shortening the useful life of the fencing. The exposed wires and the poor connection between the wires and the surrounding plastic in the above-discussed prior art references permit water to seep into the wires and cause oxidation, which drastically shortens the life span of the fencing.
Additionally, when the plastic outer layer is not well adhered to the underlying wires, the structural reinforcement provided by the wires may be lost and breakage can occur. In particular, breakage will primarily occur around the supporting brackets of the fencing where adjacent coils of fencing are joined and where abrasion can occur from contraction and expansion of the surrounding plastic relative to the underlying wiring, or from livestock rubbing the fencing. Furthermore, because the plastic will shrink a greater amount under cold conditions than will the underlying wires, it is essential that the wires and surrounding plastic be well bonded to one another. Accordingly, the object of the present invention is to overcome the above-discussed deficiencies in prior art composite metal and plastic fencing at minimal additional cost.
The above-stated object is accomplished with a composite fence assembly and method of making the same which I have invented. The composite fence assembly generally includes a plurality of spaced apart fence posts and at least one fence rail member vertically supported on the fence posts and extending between the fence posts. The at least one fence rail member further includes a plurality of (i.e., at least two) longitudinally extending fence wires, an adhesive layer adhered to each of the fence wires and a layer of synthetic resin material adhered to the fence wires by the adhesive layer. The layer of synthetic resin material encloses the fence wires and may form webs extending between the fence wires such that the fence rail member is formed.
Preferably, the fence wires are galvanized high tensile strength metal fence wires. In addition, the layer of synthetic resin material may be selected from the group consisting of polyvinyl chloride, polyethylene, polypropylene or a combination of polyethylene and polypropylene. The adhesive layer may have a thickness of between 0.001 and 0.030 of an inch on each of the fence wires. The at least one fence rail member may be vertically supported on each of the fence posts with a bracket. The fence wires may be pretensioned.
The present invention also includes a method of forming a composite fence member that includes the steps of providing at least one but generally a plurality of fence wires, straightening the plurality of fence wires, heating the fence wires, supplying or extruding an adhesive layer onto each of the fence wires and extruding a layer of synthetic resin material onto the fence wires. The fence wires are preferably heated to approximately 300xc2x0 F., and an adhesive layer is preferably added to between 0.001 and 0.030 of an inch in thickness on each of the fence wires. The layer of synthetic resin material may be extruded onto the fence wires such that the layer of synthetic resin material encloses, or encapsulates, the fence wires. The layer of synthetic resin material may form webs extending between the fence wires whereby a fence rail member is formed. The layer of synthetic resin material may be bonded to the fence wires by the adhesive layer surrounding each of the fence wires. The method may also include the step of tensioning the fence wires.
Further details and advantages of the present invention will become apparent in the following detailed description, in conjunction with the drawings, wherein like reference numerals designate like parts throughout.